Carbon sequestration is a topic receiving enormous attention in the media and among government agencies and industries involved in fossil fuel production and use. Combustion of fossil fuels is responsible for approximately 83% of greenhouse gas emissions in the U.S. Currently, the U.S. emits 6.0×109 tons carbon dioxide per year and this value is expected to increase by 27% over the next 20 years. Furthermore, the reported link between increasing concentrations of greenhouse gases such as carbon dioxide (CO2) in the atmosphere and global climate change has prompted several countries to adopt environmental standards that cap CO2 emissions and aim to reduce current emissions. Although the U.S. has not adopted a similar set of standards, in April 2007, the U.S. Supreme Court ruled that carbon dioxide was a pollutant and that the U.S. Environmental Protection Agency (U.S. EPA) has the authority and obligation to regulate carbon dioxide emissions from automobiles. Recently, the U.S. EPA has decided that carbon dioxide poses a threat to human health and the environment and that it will now be added to a list of 5 other greenhouse gases that can be regulated under the Clean Air Act. Given recent activity regarding carbon dioxide emission regulations, it is projected that the federal government may enact a carbon cap-and-trade bill. When this eventually occurs, utility companies and coal producers are in a position to be particularly affected by federal carbon dioxide regulation due to the large carbon dioxide footprint of coal-fired power plants. Although no carbon dioxide standards have been applied to power plant emissions in the U.S., plans for dozens of new coal-fired power plants have either been scrapped or delayed due to issues revolving around states concerned with future climate change legislation. Whether there is global consensus on the causes of climate change or not, it appears that carbon dioxide-emitting industries in the U.S. will soon be required to implement carbon management protocols that reduce emissions and (or) purchase or produce carbon credits.
The present invention seeks to aid the United States in the pursuit of Energy Security in an environmentally safe manner. An objective of the present invention may be to set the stage for achieving the vision of “Clean Coal” by turning carbon dioxide into a valued resource rather than a costly expense and long-term liability risk. In addition to coal, embodiments of the present invention have applications in carbon dioxide capture for fossil fuel conversion sources, natural gas-fired power plants and perhaps even distributed generation fuel cells, as well. Solving the carbon dioxide challenge for both coal and natural gas may assure the commercial viability of United States energy industries in a carbon constrained world and in turn may secure the Nation's economic prosperity.
Subsurface injection of carbon dioxide (also termed “geological carbon sequestration”) has been considered as a default method for large-scale carbon sequestration, even though the associate costs of carbon dioxide isolation and purification from flue gas, compressing, transportation, and injection are prohibitive, and little is known about the long term sustainability and potential environmental impacts. Therefore technologies that can achieve source capture and sequestration of carbon dioxide is highly desired. Technically and economically, capture and conversion of carbon dioxide in proximity of emission sources, such as power plants, can offer the most cost-effective model of sustainable carbon sequestration.
Biological techniques as represented by microalgae reactors have been investigated since the 1970s and are now implemented at pilot scale for carbon dioxide capture and conversion to biomass. Although the algae-based technology shows potential in carbon dioxide capture, it may be limited by the light source (i.e. sunlight) for photosynthesis, the primary carbon dioxide-fixation pathway in algae. Another limitation may be the large area of land required to operate the photobioreactors. These obstacles, however, may be overcome by the bacterial reactor in the various embodiments of the present invention. Bacteria may be the best candidates in bio-trapping of carbon dioxide thanks to their high reproduction rate and ubiquitous distribution.